Two loci, sapA and sapB, are involved in transpositional activation of the bgl operon in Escherichia coli. Deletion analyses and cloning experiments have located sapA next to the pgl gene and sapB near gal. The survival of bacteria carrying he drug-resistance transposons Tn5 or Tn9 on media with high concentration of kanamycin or chloramphenicol, respectively, is enhanced over 20-fold by a variety of bacterial repellants, including acetate, benzoate, salicylate and dimethyl-sulfoxide.